Late Pliocene onset of glaciation: ice-rafting and diatom stratigraphy of North Pacific DSDP cores

Abstract The revised diatom biostratigraphy for the North Pacific allows the timing of ice-rafting, as recorded in Deep Sea Drilling Project cores, to be determined. Significant ice-rafting began at the time of the Matuyama-Gauss reversal boundary, about 2.48 Ma. Other bio- and lithostratigraphic data from the Pacific, Atlantic, and Arctic Oceans, and the Black Sea all indicate that northern hemispherical cooling and the accumulation of continental ice began at 2.4–2.5 Ma. We interpret all these data to indicate northern hemisphere ice-cap formation at that time. If so, the closing of the Isthmus of Panama, approximately 3.2 m.y. ago, was not the immediate cause of the Plio-Pleistocene glaciations.